A crankshaft pulley is a pulley attached to an end of a crankshaft, which allows a belt to engage with it and serves to drive engine accessories such as a generator, a water pump, and a compressor.
A structure having a torque increasing device installed in a crankshaft pulley has been proposed. In this case, a planetary gear set may be installed inside the crankshaft pulley such that torque can be increased by the torque increasing device.
For example, when an engine starts, one of three rotary elements of the planetary gear set is restrained to increase torque being input the engine from an integrated starter generator (ISG) whereas when a motor generates electric power, rotational speeds of two rotary elements are made equal to allow the motor to generate electric power at a gear ratio of 1:1.
As a result, it is possible to cope with high engine startup torque and it is also possible to become free from limitation of the maximum rotational speed of the motor at the time of power generation so that breakage of the motor can be prevented.
However, such a torque increasing device requires a bearing between a casing and the planetary gear set to support the planetary gear set. Since the casing is fixed to an engine block, it acts as a rotational resistance body when the engine is operated and, as a result, there is a problem that power generation efficiency is lowered.
As the foregoing described as the background art is just to promote better understanding of the background of the present disclosure, it must not be taken as an admission that it corresponds to the prior art well known to those who have ordinary skill in the art.